03-02-2020 Council Work Session Packet

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Mr. Rick DeGardner February 25, 2020 Page 2 3. Water Treatment Options Upon completion of the source water analysis, we will explore available water treatment options and the recommending preferred processes for treating known and emerging contaminants that will potentially need to be treated over the anticipated life of the water treatment plant(s). The report will examine available treatment process options for identified contaminants potentially needing treatment, recommend a preferred treatment process for each identified contaminant, identify required space needs for preferred treatment processes, provide recommendation as to the required size and preferred location for the facility, and provide cost estimates for constructing and operating the facility. We will study both conventional and biological filtration and present their benefits. The iron, manganese, and ammonia in the City’s water could be treated without chlorine and potassium permanganate with biological filtration. Biological filtration is commonly practiced in the United States and Europe and is endorsed by the Minnesota Department of Health (MDH) as an efficient and effective method for treating these (and other) contaminants. The benefits of biological filtration include higher filtration rates, longer filter runs (reduces backwash supply and wastewater volumes), savings in chemical costs, and reduction in disinfection byproducts. The design of a conventional gravity filtration process with detention and aeration can easily be modified to accommodate biological filtration after the successful completion of a biological filtration study as required by MDH. WSB will coordinate and attend tours of existing water treatment facilities that utilize each of the treatment methods being evaluated so that City staff have a clear understanding of the treatment technologies and options that are available for the water treatment plant. The analysis will include, but not be limited to, initial construction costs, long term operational costs, the ability of each system to effectively and efficiently remove iron, manganese, ammonia, and other contaminants from the water supply, the discharge of the waste product, and the ability of the plant to be expanded or be modified in the future. This will be a comprehensive review and recommendation on the “best” plant to meet the current and future needs of the City. 4. Review Existing Site A potential site for the proposed water treatment plant has been identified at the southwest intersection of Birch Street and 12th Avenue South. The WSB team will visit the proposed water treatment plant site and review the existing wetlands in the area. We will also review the as-built drawings, easements, and existing infrastructure to determine if the site is feasible for further consideration for the water treatment plant. Potential contaminants and other barriers that may restrict or affect the layout of the plant at the site will be evaluated up front during this analysis. Other factors such as ease of chemical deliveries, access for maintenance trucks, security, stormwater retention, proximity to water and sanitary sewer utilities, proximity to three phase-480 volt electrical power, proximity to existing and future wells, and the potential for the City to acquire the property will be evaluated during the preliminary design phase. 5. Centralized Water Treatment Plant Preliminary Drawings We will prepare one preliminary water treatment plant floor plan drawing and one preliminary conceptual site plan drawing for a gravity filtration plant constructed at the southwest intersection of Birch Street and 12th Avenue South. The floor plan drawing will show the various recommended rooms and dimensions for the plant. The conceptual site plan will also show space for a future water treatment plant expansion.